1. Field of the Invention
This invention relates to a cleaning medium for magnetic recording devices, such as a cleaning tape, for use in cleaning of magnetic heads or movement systems of magnetic recording and reproducing devices, such as those of audio, video, or computer equipments.
2. Description of the Prior Art
In general, with magnetic recording devices utilized in video, audio, or computer equipments, the recording or reproduction of magnetic information is carried out by moving a magnetic medium, such as a magnetic tape, while it is being in sliding contact with a magnetic head. At this time, if chips having been scraped out from the magnetic tape, dust contained in the ambient air around the device, or the like, clings to the surface of the magnetic head, the reproduction output will become low and, in the worst case, no output can be obtained. In such case, a cleaning medium, such as a cleaning tape, is utilized in order to remove dirt from the surface of the magnetic head and to thereby restore the desired level of the reproduction output.
Nowadays, there is a strong demand for the recording of magnetic information at high densities. In the cases of the recording of magnetic information at high densities, the problems often occur in that, if the state of contact between the end of the magnetic head and the magnetic tape is not kept good, the recording and the reproduction of magnetic information cannot be carried out satisfactory. Therefore, besides the removal of dirt from the magnetic head, it is necessary for the cleaning tape to have the functions for trueing up the shape of the magnetic head to a certain extent. In particular, recently, magnetic heads are utilized in magnetic recording and reproducing devices for carrying out the recording of magnetic information at high densities such that the shortest recording wavelength may be at most 1 .mu.m. As for such magnetic heads, the gap length is at most 0.4 .mu.m, and therefore even slight dirt on the magnetic heads will adversely affect the recording and reproducing performance.
Also, as the material of magnetic heads, ferrite having a high surface hardness was popular in the past. However, recently, in order to achieve the recording of magnetic information at high densities, metal heads, such as Sendust heads, are used widely. The metal heads are softer and suffer from more wear than the ferrite heads. Therefore, it is important that the amount of wear of the magnetic heads due to the cleaning tape be kept small.
As for the abrasive tape for use in the polishing of magnetic heads, an abrasive tape, which comprises a non-magnetic substrate, an intermediate layer containing non-magnetic particles, and an abrasive layer containing non-magnetic abrasive particles, the intermediate layer and the abrasive layer being overlaid in this order on the non-magnetic substrate, has been disclosed in, for example, Japanese Unexamined Patent Publication No. 62 (1987)-92205. The disclosed abrasive tape employs the two-layer constitution, in which the surface of the intermediate layer is rendered rough, and in which the diameter of the abrasive particles contained in the abrasive layer overlaid upon the intermediate layer is set to be small, such that a desired level of polishing power may be obtained and the magnetic head may be prevented from being scratched. However, the disclosed abrasive tape is the one designed for the finishing polishing, and its surface roughness falls within the range of 0.03 .mu.m to 0.3 .mu.m. Therefore, the disclosed abrasive tape yields much wear of magnetic heads, is liable to cause scratches to occur on magnetic heads, and is therefore not suitable for use as a cleaning tape Abrasive tapes for magnetic heads, which are similar to the abrasive tape disclosed in the aforesaid publication, are proposed in, for example, Japanese Unexamined Patent Publication Nos. 62 (1987)-94270 and 62 (1987)-92205. Each of the proposed abrasive tapes is provided with an abrasive layer constituted of two layers. However, the proposed abrasive tapes are not suitable for carrying out the cleaning with strong cleaning power such that the magnetic heads may not be scratched.
As for the cleaning tape for magnetic heads, a cleaning tape aiming at satisfying the two requirements with respect to good cleaning characteristics and little wear of magnetic heads has been disclosed in, for example, Japanese Unexamined Patent Publication No. 6 (1994)-139531. The disclosed cleaning tape comprises a flexible substrate and two cleaning layers overlaid upon the flexible substrate, wherein the Young's modulus of the upper cleaning layer is set to be larger than the Young's modulus of the lower cleaning layer. However, the two cleaning layers of the disclosed cleaning tape contain ferromagnetic particles, and the disclosed cleaning tape cannot sufficiently satisfy the two requirements in that the cleaning tape should have strong cleaning characteristics as a whole and in that the cleaning tape should not cause scratches to occur on magnetic heads.